1. Technical Field
The present disclosure relates to an imaging device.
2. Description of the Related Art
A dynamic range of a subject existing in nature is wide. For example, an on-board imaging device is required to image a bright subject and a dark subject concurrently (wide dynamic range) since the brightness of a subject changes from moment to moment. For example, the following methods have been proposed in order to achieve a wide dynamic range.
A silicon photo diode is used in imaging devices disclosed in Japanese Unexamined Patent Application Publication No. 62-108678 and Japanese Unexamined Patent Application Publication No. 2008-99073. In Japanese Unexamined Patent Application Publication No. 62-108678, a wide dynamic range can be obtained by synthesizing images that are different in terms of an exposure period (hereinafter sometimes referred to as an “accumulation period”). This method has been already put into practical use. In Japanese Unexamined Patent Application Publication No. 2008-99073, a dynamic range is widened by synthesizing images obtained from a plurality of pixel cells having different degrees of sensitivity that are disposed in each pixel.
Japanese Unexamined Patent Application Publication No. 2007-59465 proposes a stacked sensor having a photoelectric conversion film instead of a silicon photo diode that hinders a wide dynamic range.
The aforementioned conventional imaging devices are required to be further improved in imaging in a wide dynamic range.